1. Field of the Invention
The present invention relates to a mobile communications system, a radio base station, a scheduling apparatus, a scheduling method for use with them and a program therefor, and more specifically to a packet scheduling method of a radio base station in a mobile communications system which performs packet communications.
2. Description of the Prior Art
Recently, in the mobile communications system, data communications such as electronic mail, etc. including the browsing of data and images (still images and moving pictures) over the Internet have become widespread, and the demand for data communications has increased. In the W-CDMA (Wideband Code Division Multiple Access) which is the third generation mobile communications system, the HSDPA (High Speed Downlink Packet Access) for realization of the high-speed down packet communications has been standardized in the third generation partnership project (3GPP).
In the HSDPA, the high-speed packet communications are realized in the downlink shared channel, but a radio base station is designed to improve the throughput by the user multiple effect by assigning a transmission opportunity depending on the downlink radio channel quality for a plurality of mobile stations. The method of assigning a transmission opportunity is referred to as scheduling, and can be the following method.
The PF (Proportional Fairness) system (for example, refer to Non-Patent Document 1) is a scheduling method for equally assigning a transmission opportunity to a mobile station which is awaiting the transmission of a packet. In this PF system, for example, the “instantaneous radio channel quality/average radio channel quality” of a mobile station is obtained as metric, and a transmission opportunity is assigned to a mobile station having larger metric.
Therefore, since a relative quality for the average radio channel quality is represented as an index in this PF system, a mobile station having low average radio channel quality can also be assigned a transmission opportunity.
[Non-Patent Document 1] A. Jalali et. al, “Data Throughput of CDMA-HDR a High Efficiency-High Data Rate Personal Communication Wireless System”, IEEE 51st Vehicular Technology Conference (2000)
However, in the conventional scheduling method, a transmission opportunity is assigned first to a mobile station having a larger amount of change in instantaneous radio channel quality for average radio channel quality. Therefore, a mobile station having a small change in radio channel quality is less frequently assigned a transmission opportunity although it has high radio channel quality, thereby unequally assigning a transmission opportunity.